An instrument development is proposed which will provide computerized tomographic sections using data collected within the breath-holding interval. This allows accurate abdominal tomograms to be made. A linear array, using a high-pressure Xenon multi-wire proportional chamber, simultaneously collects the data transmitted through the body by a fan beam source. This system thus provides a greater data collecting rate and eliminates the linear motion used in the EMI scanner. Reconstruction algorithms are considered which will provide increased speed and accuracy and allow data collection over limited angles. This latter property can provide tomograms of many planes of the body over and above the transverse sections. The use of different energy spectra can provide tomograms indicating the presence of specific materials. Trace amounts of relatively high atomic number materials can be detected using integrated fluorescent detection.